Radiation image capturing system

ABSTRACT

The power consumption of a battery for supplying electric power to a cassette having a radiation detector for detecting radiation image information is greatly reduced. When a cassette transceiver of the cassette starts transmitting the radiation image information to a console transceiver of a console, the cassette transceiver changes the gain of a variable-gain amplifier to change a transmission radio-wave intensity, and transmits a test signal at the changed transmission radio-wave intensity. When the console transceiver receives the test signal, the console transceiver transmits a reception acknowledgement signal generated by a reception acknowledgement signal generator. In response to the reception acknowledgement signal, the cassette transceiver sets its own transmission radio-wave intensity to a value at the time the cassette transceiver received the reception acknowledgement signal, and transmits the radiation image information at the set transmission radio-wave intensity.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application claims priority from Japanese Patent ApplicationNos. 2007- 209030, filed Aug. 10, 2007, and 2008-165207, filed Jun. 25,2008, the contents of both of which are herein incorporated by referencein their entirety.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a radiation image capturing systemhaving a cassette including a radiation detector for detecting aradiation that has passed through a subject and converting the detectedradiation into radiation image information, and an external controllerfor receiving the radiation image information transmitted from thecassette.

2. Description of the Related Art

In the medical field, there have widely been used radiation imagecapturing apparatus which apply a radiation to a subject and guide theradiation that has passed through the subject to a radiation detector,which captures a radiation image from the radiation. Known forms of theradiation detector include a conventional radiation film for recording aradiation image by way of exposure, and a stimulable phosphor panel forstoring a radiation energy representing a radiation image in a phosphorand reproducing the radiation image as stimulated light by applyingstimulating light to the phosphor. The radiation film with the recordedradiation image is supplied to a developing device to develop theradiation, or the stimulable phosphor panel is supplied to a readingdevice to read the radiation image as a visible image.

In the operating room or the like, it is necessary to read a recordedradiation image immediately from a radiation detector after theradiation image is captured for the purpose of quickly and appropriatelytreating the patient. As a radiation detector which meets such arequirement, there has been developed a radiation detector having asolid-state detector for converting a radiation directly into anelectric signal or converting a radiation into visible light with ascintillator and then converting the visible light into an electricsignal to read a detected radiation image.

Radiation image capturing systems with such a radiation detector aredisclosed in Japanese Patent No. 3494683 and Japanese Laid-Open PatentPublication No. 2006-263339.

According to Japanese Patent No. 3494683, radiation image informationdetected by a radiation detector is transmitted to a processor by way ofwireless communications, and is processed by the processor.

Japanese Laid-Open Patent Publication. No. 2006-263339 discloses anelectronic cassette capable of transmitting radiation image informationat high frequencies in excess of 1 GHz for high-speed transmission of alarge amount of image data.

However, the electronic cassette consumes a large amount of electricpower in transmitting radiation image. information to an external sourceby way of wireless communications. Therefore, a large-size battery isneeded to energize the electronic cassette, and hence the electroniccassette becomes large in volume and weight.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide a radiation imagecapturing system which consumes a reduced amount of electric power intransmitting radiation image information from a cassette to an externalsource by way of wireless communications, thereby saving electric powerof a battery.

A radiation image capturing system according to the present inventioncomprises a cassette comprising a radiation detector for detecting aradiation having passed through a subject and converting the detectedradiation into radiation image information, an image memory for storingthe converted radiation image information, a first transceiver forchanging a transmission radio-wave intensity at which a test signal orthe radiation image information stored in the image memory istransmitted to an external source by way of wireless communications, anda battery for supplying electric power to the radiation detector and thefirst transceiver, and an external controller comprising a secondtransceiver for receiving the test signal and the radiation imageinformation transmitted from the cassette and transmitting a receptionacknowledgement signal to the first transceiver, wherein when the firsttransceiver of the cassette starts transmitting the radiation imageinformation to the second transceiver of the external controller, thefirst transceiver transmits the test signal while changing thetransmission radio-wave intensity, and when the second transceiverreceives the test signal, the second transceiver transmits the receptionacknowledgement signal, and in response to the reception acknowledgementsignal, the first transceiver sets a transmission radio-wave intensityof its own to a value at the time the first transceiver received thereception acknowledgement signal, and transmits the radiation imageinformation at the set transmission radio-wave intensity.

According to the present invention, when the first transceiver of thecassette starts transmitting the radiation image information to thesecond transceiver of the external controller, the first transceivertransmits the test signal while changing the transmission radio-waveintensity, and when the second transceiver receives the test signal, thesecond transceiver transmits the reception acknowledgement signal, andin response to the reception acknowledgement signal, the firsttransceiver sets a transmission radio-wave intensity of its own to avalue at the time the first transceiver received the receptionacknowledgement signal, and transmits the radiation image information atthe set transmission radio-wave intensity. Consequently, the powerconsumption required to transmit the radiation image information fromthe first transceiver to the second transceiver is minimized, and, as aresult, the electric power stored in the battery of the cassette issaved.

When the first transceiver receives the reception acknowledgementsignal, the first transceiver may set a transmission radio-waveintensity of its own to a value which represents the sum of thetransmission radio-wave intensity at the time the first transceiverreceived the reception acknowledgement signal and a predetermined value,and may transmit the radiation image information at the set transmissionradio-wave intensity. Therefore, the first transceiver can transmit theradiation image information stably and reliably while saving theelectric power stored in the battery.

The cassette may further comprise a power switch, and the firsttransceiver may transmit the test signal when the power switch is turnedon. When the power switch is turned on, it is highly likely to capture aradiation image from then on. As the transmission radio-wave intensityis set to a minimum required when the radiation image is captured, theradiation image information can reliably be transmitted to the externalcontroller while minimizing the power consumption of the battery.

The cassette may turn off the power switch when the first transceiverfinishes transmitting the radiation image information with the powerswitch being turned on. The electric power stored in the battery is thusfurther saved.

According to the present invention, since the power consumption requiredto transmit the radiation image information from the cassette to theexternal controller by way of wireless communications can be reduced,the electric power stored in the battery which energizes the cassette issaved.

The above and other objects, features, and advantages of the presentinvention will become more apparent from the following description whentaken in conjunction with the accompanying drawings in which preferredembodiments of the present invention are shown by way of illustrativeexample.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of an operating room incorporating aradiation image capturing system according to an embodiment of thepresent invention;

FIG. 2 is a perspective view, partly cut away, showing internalstructural details of a radiation detecting cassette according to thepresent invention;

FIG. 3 is a block diagram of a circuit arrangement of a radiationdetector of the radiation detecting cassette shown in FIG. 2;

FIG. 4 is a block diagram of the radiation image capturing system shownin FIG. 1;

FIG. 5 is a block diagram of a radiation image information transmittingand receiving system as part of the radiation image capturing systemaccording to the embodiment of the present invention;

FIG. 6 is a flowchart of an operation sequence of the radiation imagecapturing system:

FIG. 7 is a block diagram of a radiation image capturing systemaccording to another embodiment of the present invention

FIG. 8 is a perspective view showing a radiation detecting cassette inthe radiation image capturing system according to another embodiment ofthe present invention; and

FIG. 9 is a perspective view showing a cradle which charges theradiation detecting cassette.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

As shown in FIG. 1, an operating room 12 incorporates a radiation imagecapturing system 10 according to a preferred embodiment of the presentinvention. The operating room 12 has, in addition to the radiation imagecapturing system 10, a surgical table 16 for a patient 14 to liethereon, and an instrument table 20 disposed on one side of the surgicaltable 16 for placing thereon various tools and instruments to be used bysurgeons 18 for operating the patient 14. The surgical table 16 issurrounded by various apparatus required for surgical operations,including an anesthesia apparatus, an aspirator, an electrocardiograph,a blood pressure monitor, etc.

The radiation image capturing system 10 includes an image capturingapparatus 22 for irradiating the patient 14 as a subject with aradiation X at a dose according to image capturing conditions, acassette (radiation detecting cassette) 24 housing therein a radiationdetector, to be described later, for detecting the radiation X that haspassed through the patient 14, a display device 26 for displaying aradiation image based on the radiation X that is detected by theradiation detector, and a console (an external controller for thecassette 24) 28 for controlling the image capturing apparatus 22, thecassette 24, and the display device 26. The console 28, the imagecapturing apparatus 22, the cassette 24, and the display device 26 sendand receive signals by way of wireless communications indicated by thebroken lines.

The image capturing apparatus 22 is coupled to a universal arm 30 so asto be movable to a desired position for capturing a desired area of thepatient 14 and also to be retractable to a position out of the way whilethe surgeons 18 are performing a surgical operation on the patient 14.Similarly, the display device 26 is coupled to a universal arm 32 so asto be movable to a position where the surgeons 18 can easily confirm acaptured radiation image displayed on the display device 26.

FIG. 2 shows in perspective internal structural details of the cassette24. As shown in FIG. 2, the cassette 24 has a casing 34 made of amaterial permeable to the radiation X. The casing 34 houses therein agrid 38 for removing scattered rays of the radiation X from the patient14, a radiation detector 40 for detecting the radiation X that haspassed through the patient 14, and a lead plate 42 for absorbing backscattered rays of the radiation X, which are successively arranged inthe order named from a surface 36 of the casing 34 which is irradiatedwith the radiation X. The irradiated surface 36 of the casing 34 may beconstructed as the grid 38.

The casing 34 also houses therein a battery 44 as a power supply of theradiation detecting cassette 24, the battery 44 having a voltage Vcc, acassette controller 46 for energizing the radiation detector 40 withelectric power supplied from the battery 44, and a cassette transceiver(first transceiver) 48 for sending and receiving signals including theinformation of the radiation X detected by the radiation detector 40, toand from the console 28. A shield plate of lead or the like shouldpreferably be placed over the side surfaces of the cassette controller46 and the transceiver 48 under the irradiated surface 36 of the casing34 to protect the cassette controller 46 and the transceiver 48 againstdamage which would otherwise be caused if irradiated with the radiationX.

FIG. 3 shows in block form a circuit arrangement of the radiationdetector 40. As shown in FIG. 3, the radiation detector 40 comprises anarray of thin-film transistors (TFTs) 52 arranged in rows and columns, aphotoelectric conversion layer 51 made of a material such as amorphousselenium (a-Se) for generating electric charges upon detection of theradiation X, the photoelectric conversion layer 51 being disposed on thearray of TFTs 52, and an array of storage capacitors 53 connected to thephotoelectric conversion layer 51. When the radiation X is applied tothe radiation detector 40, the photoelectric conversion layer 51generates electric charges, and the storage capacitors 53 store thegenerated electric charges. Then, the TFTs 52 are turned on along eachrow at a time to read the electric charges from the storage capacitors53 as an image signal. In FIG. 3, the photoelectric conversion layer 51and one of the storage capacitors 53 are shown as a pixel 50, and thepixel 50 is connected to one of the TFTs 52. Details of the other pixels50 are omitted from illustration. Since amorphous selenium tends tochange its structure and lose its function at high temperatures, itneeds to be used in a certain temperature range. Therefore, some meansfor cooling the radiation detector 40 should preferably be provided inthe cassette 24.

The TFTs 52 connected to the respective pixels 50 are connected torespective gate lines 54 extending parallel to the rows and respectivesignal lines 56 extending parallel to the columns. The gate lines 54 areconnected to a line scanning driver 58, and the signal lines 56 areconnected to a multiplexer 66 serving as a reading circuit.

The gate lines 54 are supplied with control signals Von, Voff forturning on and off the TFTs 52 along the rows from the line scanningdriver 58. The line scanning driver 58 comprises a plurality of switchesSW1 for switching between the gate lines 54 and an address decoder 60for outputting a selection signal for selecting one of the switches SW1at a time. The address decoder 60 is supplied with an address signalfrom the cassette controller 46.

The signal lines 56 are supplied with electric charges stored in thestorage capacitors 53 of the pixels 50 through the TFTs 52 arranged inthe columns. The electric charges supplied to the signal lines 56 areamplified by amplifiers 62 connected respectively to the signal lines56. The amplifiers 62 are connected through respective sample and holdcircuits 64 to the multiplexer 66. The multiplexer 66 comprises aplurality of switches SW2 for successively switching between the signallines 56 and an address decoder 68 for outputting a selection signal forselecting one of the switches SW2 at a time. The address decoder 68 issupplied with an address signal from the cassette controller 46. Themultiplexer 66 has an output terminal connected to an A/D converter 70.A radiation image signal generated by the multiplexer 66 based on theelectric charges from the sample and hold circuits 64 is converted bythe A/D converter 70 into a digital image signal representing radiationimage information, which is supplied to the cassette controller 46.

FIG. 4 shows in block form the radiation image capturing system 10 whichcomprises the image capturing apparatus 22, the cassette 24, the displaydevice 26, and the console 28. The console 28 is connected to aradiology information system (RIS) 29 which generally manages radiationimage information handled by the radiological department of the hospitaland other information. The RIS 29 is connected to a hospital informationsystem (HIS) 31 which generally manages medical information in thehospital.

The image capturing apparatus 22 comprises an image capturing switch 72,a radiation source 74 for outputting the radiation X, a transceiver 76for receiving image capturing conditions from the console 28 by way ofwireless communications and transmitting an image capturing completionsignal, etc. to the console 28 by way of wireless communications, and aradiation source controller 78 for controlling the radiation source 74based on an image capturing start signal supplied from the imagecapturing switch 72 and image capturing conditions supplied from thetransceiver 76.

The cassette 24 houses therein the radiation detector 40, the battery44, the cassette controller 46, the cassette transceiver 48, and a powerswitch 45. The power switch 45 is turned on and off manually or by aswitch control signal Ss from the cassette transceiver 48, forselectively supplying electric power from the battery 44 to theradiation detector 40, the cassette controller 46, and the cassettetransceiver 48. The cassette controller 46 comprises an address signalgenerator 80 for supplying address signals to the address decoder 60 ofthe line scanning driver 58 and the address decoder 68 of themultiplexer 66 of the radiation detector 40, an image memory 82 forstoring the radiation image information detected by the radiationdetector 40, a cassette ID memory 84 for storing cassette ID informationfor identifying the cassette 24, and an image compressor(amount-of-information reducing means), not shown, for compressing theradiation image information stored in the image memory 82 to reduce theamount of the radiation image information.

The cassette transceiver 48 receives a reception acknowledgement signal,to be described later, from the console 28 by way of wirelesscommunications and transmits the cassette ID information stored in thecassette ID memory 84 and the radiation image information stored in theimage memory 82 to the console 28 by way of wireless communications.

The display device 26 comprises a receiver 90 for receiving theradiation image information from the console 28, a display controller 92for controlling the display of the received radiation image information,and a display unit 94 for displaying the radiation image informationprocessed by the display controller 92.

The console 28 comprises a console transceiver (second transceiver) 96for transmitting and receiving necessary information including radiationimage information to and from the image capturing apparatus 22, thecassette 24, and the display device 26 by way of wirelesscommunications, an image capturing condition manager 98 for managingimage capturing conditions required for the image capturing apparatus 22to capture radiation images, an image processor (image processing means)100 for processing radiation image information transmitted from thecassette 24, an image memory 101 for storing the radiation imageinformation processed by the image processor 100, a patient informationmanager 102 for managing patient information of the patient 14 whoseimages are to be captured, and a cassette information manager 104 formanaging cassette information transmitted from the cassette 24.

The console 28 may be located outside of the operating room 12 insofaras it can transmit and receive signals to and from the image capturingapparatus 22, the cassette 24, and the display device 26 by way ofwireless communications.

The image capturing conditions refer to condition for determining a tubevoltage, a tube current, an irradiation time, etc. required to apply aradiation X at an appropriate dose to an area to be imaged of thepatient 14. The image capturing conditions may include an area to beimaged of the patient 14, an image capturing method, etc., for example.The patient information refers to information for identifying thepatient 14, such as the name, gender, patient ID number, etc. of thepatient 14. Ordering information for ordering the capture of an image,including the image capturing conditions and the patient information canbe set directly on the console 28 or can be supplied from an externalsource to the console 28 via the RIS 29. The cassette information refersto cassette ID information for identifying the cassette 24.

FIG. 5 shows in block form a radiation image information transmittingand receiving system 110 as part of the cassette transceiver 48 and theconsole transceiver 96.

As shown in FIG. 5, the cassette transceiver 48 comprises a cassettetransceiver controller 202 having a microcomputer, an antenna 203, anantenna sharing unit 205, a receiver 208, a transmitter 210, and avariable-gain amplifier 212.

The cassette transceiver controller 202 comprises a test signalgenerator 204, a transmission radio-wave intensity changer 206, and atransmission radio-wave intensity setting unit 207.

The receiver 208 receives a radio wave (RF (radio-frequency) signal)received by the antenna 203 through the antenna sharing unit 205,converts the received RF signal into an intermediate-frequency (IF)signal, demodulates the IF signal, and outputs the demodulated signal asreception data to the cassette transceiver controller 202. Thetransmitter 210 modulates data (radiation image information) read fromthe image memory 82 (see FIG. 4) or a test signal output from the testsignal generator 204, and converts the modulated signal from an IFsignal into an RF signal.

The test signal generator 204 supplies a test signal to the transmitter210 at the time it detects when the power switch 45 is turned on.

The transmission radio-wave intensity changer 206 outputs avariable-gain control signal Sc to a control signal port of thevariable-gain amplifier 212. The variable-gain control signal Sc enablesthe variable-gain amplifier 212 to amplify the test signal output fromthe transmitter 210 into a transmission signal St (proportional to atransmission radio wave) which is of a value increased stepwise from aminimum value.

As described later, when the power switch 45 is turned on, thetransmission radio-wave intensity setting unit 207 stores thevariable-gain control signal Sc for achieving the radio-wave intensityof the transmission signal St (proportional to a transmission radiowave) which has been determined by the transmission radio-wave intensitychanger 206.

The transmission signal St is supplied through the antenna sharing unit205 to the antenna 203, which transmits the transmission signal St as atransmission ratio wave.

The console transceiver 96 comprises a console transceiver controller220 having a microcomputer, an antenna 224, an antenna sharing unit 226,a receiver 228, and a transmitter 230.

The console transceiver controller 220 has a reception acknowledgementsignal generator 232. The receiver 228 receives a radio wave (RF signal)received by the antenna 224 through the antenna sharing unit 226,converts the received RF signal into an intermediate-frequency (IFsignal) signal, demodulates the IF signal, and outputs the demodulatedsignal as reception data to the console transceiver controller 220. Thedemodulated reception data include a test signal or radiation imageinformation.

When the reception acknowledgement signal generator 232 receives thetest signal, it generates a reception acknowledgement signal andsupplies the reception acknowledgement signal through the transmitter230 and the antenna sharing unit 205 to the antenna 224, which transmitsthe reception acknowledgement signal as a radio wave.

The radiation image capturing system 10 according to the presentembodiment is basically constructed as described above, and operation ofthe radiation image capturing system 10 will be described below withreference to a flowchart shown in FIG. 6.

The radiation image capturing system 10 is installed in the operatingroom 12 and used when a radiation image of the patient 14 is required bythe surgeons 18 who are performing an operation on the patient 14.Before a radiation image of the patient 14 is captured, patentinformation of the patient 14 to be imaged is registered in the patientinformation manager 102 of the console 28. If an area to be imaged ofthe patient 14 and an image capturing method have already been known,they are previously registered as image capturing conditions in theimage capturing condition manager 98. After the above preparatoryprocess is finished, the surgeons 18 perform an operation on the patient14.

For capturing a radiation image of the patient 14 during the operation,one of the surgeons 18 or the radiological technician places thecassette 24 on a predetermined position between the patient 14 and thesurgical table 16 with the irradiated surface 36 facing the imagecapturing apparatus 22, and turns on the power switch 45.

In step S1, the cassette transceiver controller 202 of the cassettetransceiver 48 detects when the power switch 45 is turned on.

In step S2, the transmission radio-wave intensity changer 206 suppliesthe variable-gain amplifier 212 with a variable-gain control signal Scfor setting the transmission radio-wave intensity to a minimum level.

In step S3, the test signal generator 204 generates a test signalcomprising a unique word and outputs the test signal to the transmitter210. The test signal is supplied from the transmitter 210 to thevariable-gain amplifier 212, which amplifies the test signal. Theamplified test signal is supplied as a transmission signal Strepresenting the minimum radio-wave intensity through the antennasharing unit 205 to the antenna 203, which transmits the transmissionsignal St as a radio wave.

In step S4, a timing means (timer), not shown, monitors for a givenperiod of time whether the cassette transceiver 48 has received areception acknowledgement signal indicating that the console transceiver96 has received the test signal or not.

If the cassette transceiver 48 has not received a receptionacknowledgement signal within the given period of time in step S4, thenthe transmission radio-wave intensity changer 206 increases thetransmission radio-wave intensity by a certain level, and the cassettetransceiver 48 transmits a test signal at the increased transmissionradio-wave intensity level as a transmission signal St. In this manner,unless the cassette transceiver 48 receives a reception acknowledgementsignal, it transmits a test signal at a transmission radio-waveintensity level increased stepwise as a transmission signal St.

In step S11, the console transceiver controller 220 of the consoletransceiver 96 monitors at all times whether it has received a testsignal or not.

If the console transceiver controller 220 confirms that it has receiveda test signal in step S11, the reception acknowledgement signalgenerator 232 generates a reception acknowledgement signal in step S12,and transmits the reception acknowledgement signal through thetransmitter 230, the antenna sharing unit 226, and the antenna 224.

At this time, in step S4, the cassette transceiver controller 202 of thecassette transceiver 48 confirms the reception of the receptionacknowledgement signal.

In step S5, the cassette transceiver controller 202 stores thevariable-gain control signal Sc (the value thereof), representing itsown transmission radio-wave intensity, which has been set in thevariable-gain amplifier 212 at the time it has received the receptionacknowledgement signal, in the transmission radio-wave intensity settingunit 207.

Consequently, when a signal radio wave representing radiation imageinformation is transmitted from the cassette 24, the signal radio-waveintensity thereof is held to a minimum (required minimum), and the powerconsumption of the battery 44 of the cassette 24 is reduced.

The variable-gain control signal Sc (the value thereof) set in thetransmission radio-wave intensity setting unit 207 may be the sum of thevariable-gain control signal Sc (the value thereof) which has been setin the variable-gain amplifier 212 at the time it received the receptionacknowledgement signal, and a certain value. In this manner, thecassette transceiver 48 is capable of reliably transmitting radiationimage information while saving the electric power stored in the battery44.

Then, after having moved the image capturing apparatus 22 to a positionconfronting the radiation detecting cassette 24, one of the surgeons 18or the radiological technician turns on the image capturing switch 72.

When the image capturing switch 72 is turned on, the radiation sourcecontroller 78 of the image capturing apparatus 22 acquires the imagecapturing conditions with respect to the area to be imaged of thepatient 14 from the image capturing condition manager 98 of the console28 by way of wireless communications via the console transceiver 96 andthe transceiver 76. The radiation source controller 78 controls theradiation source 74 to apply a radiation X at a given dose to thepatient 14 according to the acquired image capturing conditions.

The radiation X which has passed through the patient 14 is applied tothe grid 38, which removes scattered rays of the radiation X. Then, theradiation X is applied to the radiation detector 40, and converted intoelectric signals by the photoelectric conversion layer 51 of the pixels50 of the radiation detector 40. The electric signals are stored aselectric charges in the storage capacitors 53 (see FIG. 3). The storedelectric charges, which represent radiation image information of thepatient 14, are read from the storage capacitors 53 according to addresssignals which are supplied from the address signal generator 80 of thecassette controller 46 to the line scanning driver 58 and themultiplexer 66.

Specifically, in response to the address signal supplied from theaddress signal generator 80, the address decoder 60 of the line scanningdriver 58 outputs a selection signal to select one of the switches SW1,which supplies the control signal Von to the gates of the TFTs 52connected to the gate line 54 corresponding to the selected switch SW1.In response to the address signal supplied from the address signalgenerator 80, the address decoder 68 of the multiplexer 66 outputs aselection signal to successively turn on the switches SW2 to switchbetween the signal lines 56 for thereby reading radiation imageinformation represented by the electric charges stored in the storagecapacitors 53 of the pixels 50 connected to the selected gate line 54,through the signal lines 56.

The radiation image information (electric charges) read from the storagecapacitors 53 of the pixels 50 connected to the selected gate line 54are amplified by the respective amplifiers 62, sampled by the sample andhold circuits 64, and supplied to the multiplexer 66. Based on thesupplied electric charges, the multiplexer 66 generates and supplies aradiation image signal to the A/D converter 70, which converts theradiation image signal into a digital signal. The digital signal whichrepresents the radiation image information is stored in the image memory82 of the cassette controller 46.

Similarly, the address decoder 60 of the line scanning driver 58successively turns on the switches SW1 to switch between the gate lines54 according to the address signal supplied from the address signalgenerator 80. The electric charges serving as radiation imageinformation stored in the storage capacitors 53 of the pixels 50connected to the successively selected gate lines 54 are read throughthe signal lines 56, and processed by the multiplexer 66 and the A/Dconverter 70 into digital signals, which are stored in the image memory82 of the cassette controller 46.

In step S6, the radiation image information stored in the image memory82 is read from the image memory 82 and transmitted to the console 28 ata minimum transmission radio-wave intensity level based on thevariable-gain control signal Sc which has already been set in thecontrol signal port of the variable-gain amplifier 212 through thetransmission radio-wave intensity setting unit 207 via the cassettetransceiver 48 by way of wireless communications, or at a transmissionradio-wave intensity level close to the minimum transmission radio-waveintensity level.

The radiation image information transmitted to the console 28 isreceived by the console transceiver 96, processed by the image processor100, and then stored in the image memory 101 in association with thepatient information of the patient 14 registered in the patientinformation manager 102.

The radiation image information processed by the image processor 100 istransmitted from the console transceiver 96 to the display device 26. Inthe display device 26, the receiver 90 receives the radiation imageinformation, and the display controller 92 controls the display unit 94to display a radiation image based on the radiation image information.

When the completion of the transmission of the radiation imageinformation is confirmed in step S6, the cassette transceiver controller202 sends the switch control signal Ss to turn off the power switch 45.Therefore, the cassette 24 is prevented from being left in a standbymode in which a certain amount electric power is consumed with the powerswitch 45 being turned on. Thus, electrical power saving of the battery44 is further facilitated.

In the radiation image capturing system 10 according to the presentembodiment, the cassette 24 has the radiation detector 40 for detectingthe radiation X that has passed through the patient 14 as a subject andconverting the radiation X into radiation image information, the imagememory 82 for storing the converted radiation image information, thecassette transceiver 48 as the first transceiver for changing thetransmission radio-wave intensity at which the test signal or theradiation image information stored in the image memory 82 is transmittedto the external source by way of radio communications, and the battery44 for supplying electric power to the radiation detector 40 and thecassette transceiver 48. The radiation image capturing system 10 has theconsole 28 as the external controller having the console transceiver 96as the second transceiver for receiving the test signal and theradiation image information transmitted from the cassette 24 andtransmitting the reception acknowledgement signal to the cassettetransceiver 48.

When the cassette transceiver 48 of the cassette 24 starts transmittingthe radiation image information to the console transceiver 96 of theconsole 28, the cassette transceiver 48 changes the gain of thevariable-gain amplifier 212 stepwise from a minimum value to change thetransmission radio-wave intensity, and transmits the test signal as thetransmission signal St at the changed transmission radio-wave intensity.When the console transceiver 96 receives the transmission signal St asthe test signal at the changed transmission radio-wave intensity, theconsole transceiver 96 transmits the reception acknowledgement signalgenerated by the reception acknowledgement signal generator 232 to thecassette transceiver 48. In response to the reception acknowledgementsignal, the cassette transceiver 48 sets its own transmission radio-waveintensity to the value at the time it received reception acknowledgementsignal, and transmits the radiation image information at the settransmission radio-wave intensity. Therefore, the power consumption fortransmitting the radiation image information from the cassettetransceiver 48 to the console transceiver 96 is minimized, and theelectric power stored in the battery 44 of the cassette 24 is greatlysaved.

When the cassette transceiver 48 receives the reception acknowledgementsignal, it sets its own transmission radio-wave intensity to the valuerepresenting the sum of the transmission radio-wave intensity at thetime it received the reception acknowledgement signal and a certainvalue, and transmits the radiation image information at the settransmission radio-wave intensity. Therefore, the cassette transceiver48 can transmit the radiation image information stably and reliablywhile saving the electric power stored in the battery 44.

Inasmuch as the transmission signal St as the test signal is transmittedwhen the power switch 45 is turned on, the radiation image informationcan reliably be transmitted to the console transceiver 96 when theradiation image information is stored in the image memory 82 of thecassette 24. Since the power switch 45 is turned off when thetransmission of the radiation image information is finished, theelectric power stored in the battery 44 is further saved.

According to the present embodiment, the power consumption at the timethe radiation image information is transmitted from the cassette 24 tothe console 28 by way of wireless communications is held to a minimumrequired. Consequently, the electric power of the battery 44 forenergizing the cassette 24 can be saved.

Prior to starting to capture a radiation image of the patient 14, thepower switch 45 may be turned on in step S1 by wireless communicationswhen, as shown in FIG. 7, one of the surgeons 18 or the radiologicaltechnician holds an RFID (Radio-Frequency IDentification) card 304certified for the identification thereof over an RFID card signalreceiver (RFID transceiver) 302 on the cassette 24.

In the radiation image capturing system 10 according to the illustratedembodiment, the radiation detector 40 housed in the cassette 24 directlyconverts the dose of the applied radiation X into an electric signalwith the photoelectric conversion layer 51. However, the radiation imagecapturing system 10 may employ a radiation detector including ascintillator for converting the applied radiation X into visible lightand a solid-state detecting device such as of amorphous silicon (a-Si)or the like for converting the visible light into an electric signal(see Japanese Patent No. 3494683).

Alternatively, the radiation image capturing system 10 may employ alight-conversion radiation detector for acquiring radiation imageinformation. The light-conversion radiation detector operates asfollows: When a radiation is applied to a matrix of solid-statedetecting devices, the solid-state detecting devices store anelectrostatic latent image depending on the dose of the appliedradiation. For reading the stored electrostatic latent image, readinglight is applied to the solid-state detecting devices to cause thesolid-state detecting devices to generate an electric currentrepresenting radiation image information. When erasing light is appliedto the radiation detector, radiation image information representing aresidual electrostatic latent image is erased from the radiationdetector, which can thus be reused (see Japanese Laid-Open PatentPublication No. 2000-105297).

When the cassette 24 is used in the operating room 12 or the like, thecassette 24 may be subjected to adhesion of blood, contamination, etc.However, when the cassette 24 is designed to have a waterproof andhermetically-sealed structure, and is sterilized and cleaned asnecessary, one cassette 24 can be used repeatedly.

The cassette 24 is not limited to use in the operating room 12, and maybe used for a medical examination and a round in the hospital.

Also, the cassette 24 may communicate with external devices via opticalwireless communication using infrared light or the like, instead ofgeneral wireless communication using radio wave.

Preferably, the cassette 500 may be constructed as shown in FIG. 8.

Specifically, the cassette 500 includes a guiding line 504 drawn on theradiation-irradiated surface of a casing 502, the guiding line 504serving as a reference for setting a captured area and a capturedposition. Using the guiding line 504, a subject such as a patient 14 canbe positioned with respect to the cassette 500, and an area irradiatedwith radiation X can be set, thereby recording radiation imageinformation on an appropriate captured area.

The cassette 500 is provided with a display section 506 on an areathereof other than the captured area, for displaying various informationabout the cassette 500. The information which is displayed on thedisplay section 506, includes ID information of a subject such as apatient 14 whose radiation image information is to be recorded on thecassette 500, the number of times the cassette 500 has been used, anaccumulated exposed radiation dose, a charging state (remaining batterylevel) of a battery 44 in the cassette 500, image capturing conditionsof radiation image information, and a positioning image of the subjectsuch as the patient 14 with respect to the cassette 500. In this case, atechnician confirms a subject such as a patient 14 based on the IDinformation displayed on the display section 506, for example, and alsopreviously confirms that the cassette 500 is placed in a usable state.Then, the technician positions a desired captured area of the subjectsuch as the patient 14 with respect to the cassette 500 based on thedisplayed positioning image, thereby capturing appropriate radiationimage information.

Also, the cassette 500 is provided with a handgrip 508, whereby it iseasier to handle and carry the cassette 500.

Preferably, the cassette 500 may have, on a side thereof, an inputterminal 510 for an AC adapter, a USB (Universal Serial Bus) terminal512, and a card slot 516 for inserting a memory card 514.

When the charging function of the battery 44 in the cassette 500 becomesdeteriorated, or when there is not enough time to fully charge thebattery 44, the input terminal 510 is connected to the AC adapter toexternally supply the cassette 500 with electric power, thereby enablingthe cassette 500 to be used immediately.

The USB terminal 512 or the card slot 516 may be used when the cassette500 cannot transmit and receive information to and from external devicessuch as the console 28 via wireless communication. Specifically, byconnecting a cable to the USB terminal 512, the cassette 500 cantransmit and receive information to and from the external devices viawire communication. Alternatively, the memory card 514 is inserted intothe card slot 516, and necessary information is recorded on the memorycard 514. After that, the memory card 514 is removed from the card slot516, and the memory card 514 is inserted into the external device,thereby enabling information to be transferred.

Preferably, a cradle 518 may be disposed in the operating room 12 or ata desired place in the hospital, into which the cassette 24 is insertedto charge the internal battery 44, as shown in FIG. 9. In this case, inaddition to charging the battery 44, the cradle 518 may transmit andreceive necessary information to and from external devices such as HIS31, RIS 29, the console 28, etc. by way of wireless or wirecommunications of the cradle 518. The information may include radiationimage information which is recorded on the cassette 24 inserted into thecradle 518.

Also, the cradle 518 may be provided with a display section 520. Thedisplay section 520 may display necessary information including acharging state of the inserted cassette 24 and radiation imageinformation acquired from the cassette 24.

Further, a plurality of cradles 518 may be connected to a network. Inthis case, information about charging states of cassettes 24 inserted inrespective cradles 518 can be collected through the network, and thecassette 24 in a usable state can be located.

Although certain preferred embodiments of the present invention havebeen shown and described in detail, it should be understood that variouschanges and modifications may be made therein without departing from thescope of the appended claims.

1. A radiation image capturing system comprising: a cassette comprisinga radiation detector for detecting a radiation having passed through asubject and converting the detected radiation into radiation imageinformation, an image memory for storing the converted radiation imageinformation, a first transceiver for changing a transmission radio-waveintensity at which a test signal or the radiation image informationstored in said image memory is transmitted to an external source by wayof wireless communications, and a battery for supplying electric powerto said radiation detector and said first transceiver; and an externalcontroller comprising a second transceiver for receiving the test signaland the radiation image information transmitted from said cassette andtransmitting a reception acknowledgement signal to said firsttransceiver; wherein when said first transceiver of said cassette startstransmitting the radiation image information to said second transceiverof said external controller, said first transceiver transmits said testsignal while changing the transmission radio-wave intensity, and whensaid second transceiver receives said test signal, said secondtransceiver transmits said reception acknowledgement signal, and inresponse to said reception acknowledgement signal, said firsttransceiver sets a transmission radio-wave intensity of its own to avalue at the time said first transceiver received said receptionacknowledgement signal, and transmits the radiation image information atthe set transmission radio-wave intensity.
 2. A radiation imagecapturing system according to claim 1, wherein when said firsttransceiver receives said reception acknowledgement signal, said firsttransceiver sets a transmission radio-wave intensity of its own to avalue which represents the sum of the transmission radio-wave intensityat the time said first transceiver received said receptionacknowledgement signal and a predetermined value, and transmits theradiation image information at the set transmission radio-waveintensity.
 3. A radiation image capturing system according to claim 1,wherein said cassette further comprises a power switch, and said firsttransceiver transmits said test signal when said power switch is turnedon.
 4. A radiation image capturing system according to claim 3, whereinsaid cassette turns off said power switch when said first transceiverfinishes transmitting the radiation image information with said powerswitch being turned on.
 5. A radiation image capturing system accordingto claim 3, wherein said cassette further comprises an RFID card signalreceiver for turning on said power switch when a certified RFID card isheld over said RFID card signal receiver.
 6. A radiation image capturingsystem according to claim 1, further comprising: an image capturingapparatus for applying said radiation at a dose according to imagecapturing conditions to said subject; wherein said external controllercomprises a console for supplying said image capturing conditions tosaid image capturing apparatus.
 7. A radiation image capturing systemaccording to claim 6, wherein said console supplies said image capturingconditions to said image capturing apparatus via said second transceiverby way of wireless communications.
 8. A method of setting a transmissionradio-wave intensity in a wireless radiation image capturing system fortransmitting radiation image information from a cassette transceiver ofa cassette having a radiation detector for detecting a radiation havingpassed through a subject and converting the detected radiation intoradiation image information, to a console transceiver of a console, saidmethod comprising the steps of: transmitting a test signal at a changedtransmission radio-wave intensity from said cassette transceiver;transmitting a reception acknowledgement signal from said consoletransceiver when said console transceiver receives the test signal; andin response to the reception acknowledgement signal, setting thetransmission radio-wave intensity of said cassette transceiver to avalue at the time said cassette transceiver received the receptionacknowledgement signal, and transmitting the radiation image informationfrom said cassette transceiver at the set transmission radio-waveintensity.